Brine trucks were out in Northern Virginia on Thursday, but there was no snow in the forecast at that point. (Robert Thompson/The Washington Post)

You may have seen brine trucks on Wednesday and Thursday in Northern Virginia, or maybe those white, salty lines on the road that portend winter storms. But because — as of Thursday, at least — we don’t expect wintry weather in the next week or so, lots of readers have asked why they’re going through the trouble. What did they know that we don’t, or didn’t they get the message?

I thought I had an idea what was going on, but I wanted to go straight to the source at VDOT to confirm. Ellen Kamilakis is the senior public affairs officer for the Northern Virginia district. She runs their active and informative Twitter account. We talked shop about snow, trucks, brine and planning. It was very interesting.

Earlier this week, we were seeing a possible storm on Sunday. Come Wednesday morning, the models started to back off that idea, and by Thursday, it was gone. Virginia made the decision to brine on Wednesday, when things were still uncertain, but called it off on Thursday. (The Capital Weather Gang didn’t pull the plug on the wintry weather forecast until Thursday, as well.)

Road maintenance decisions are made days in advance — even when the forecast is uncertain. They can’t just put the decision off until meteorologists know without a shadow of a doubt that it is/is not going to snow.

“It’s like an aircraft carrier,” Kamilakis said. “You can’t turn an aircraft carrier around on a dime.”

Their process is pretty straightforward. When they see the potential for precipitation and cold road temperatures, they have to make a call on whether to treat the roads. There’s no specific criterion for the decision, because every storm is different. If the answer is yes, then they do it on a route-by-route basis, beginning with the most affected routes: highways, main thoroughfares, bridges.

And it’s on a contract basis. They contract the work out, route by route, which means if the forecast changes, they can halt the treatment operation.

That’s what happened this week. VDOT saw a threat, made the decision to pre-treat and then called it off when the forecast turned “all clear.”

Kamilakis mentioned Jan. 20 and Dec. 17, 2016 — both of which were significant ice events because of road temperatures — as dates she keeps in mind when she tries to explain their road treatment decisions.

“Our primary concern is public safety,” Kamilakis said. “There was a possibility of wintry mix on Sunday, with very low temperatures that will also drop road temps.”

She said that’s what they were the most concerned about — not the threat of snow or a big winter storm, but overnight temperatures that would be low enough to push the roads below freezing. If that happened, any light precipitation on Sunday would have the potential to freeze.

Other interesting things I learned:

  • There is no such thing as “use it or lose it.” Road treatment falls under road maintenance in Virginia, which means that if they don’t use the money for salt and plows, they will use it for things like potholes and tree-branch trimming. So there’s no pressure to use a certain amount on winter-weather preparation. Snow treatment is $82.7 million of the road maintenance budget.
  • There’s also no reason to use the salt or brine. They make the brine on a case-by-case basis, too. They mix it up as it’s needed. And if they don’t use it, they can store it and use it later.
  • When you see salt trucks or plows on the side of the road, it’s probably because they hit their time limit. They can drive only for so long, by law, before they have to stop and rest. And they will pull over and sleep wherever, because when their “break time” is up, they’ll want to get right back to treating the roads.
  • Some people assumed this week’s pretreatment was an overtime issue: that VDOT would rather pre-treat early than pay overtime on the weekends. Kamilakis said she has no idea where that came from, as VDOT crews are contracted.

Here’s the explanation she posted on Twitter Friday morning after the questions began streaming in: